REVIEW : ECOLOGY UNIT
A. Top “5” — If you learned anything from this unit, you should have learned:
1. Populations
group of individuals of same species living in same area (size, density,
distribution/dispersion)
habitat (type of area organism lives) vs. niche (role in ecosystem)
competition
a. survivorship curves
Type 1 = most live long life = K-selected = humans, large mammals
Type 2 = constant death rate = hydra, small mammals
Type 3 = most die young = r-selected opportunists = fish, shellfish
b. age structure (rapid growth vs. declining vs. stable populations)
c. population growth
biotic potential (max. growth rate under ideal conditions)
– consider such things as: age at reproductive maturity, offspring quantity, frequency
of reproduction, reproductive lifetime, survivorship of offspring
limiting factors
– density dependent (competition for resources, parasites & diseases, waste
products, stress, predation)
– density independent (climate = temperature & rainfall, natural disaster)
exponential growth (J-shaped, unlimited) vs. logistic growth curve (S-shaped, limited)
carrying capacity = maximum population supported by habitat
population cycles
-Methods of estimating populations
d. human population growth
exponential – reasons for this pattern
2. Communities
interaction of populations
a. interspecific competition
competitive exclusion principle
resource partitioning
character displacement
keystone species
– important regulating effect on community, maintains diversity
b. symbiosis = species interaction
– mutualism +/+
– commensalism +/0
– parasitism +/– ; parasite vs. parasitoid
– predation +/–
– competition –/– (interspecific vs. intraspecific)
c. coevolution
defense mechanisms
– camouflage (cryptic coloration)
– warning coloration (aposematic coloration)
– mimicry
o Batesian = harmless copies harmful
o Mullerian = warning both are harmful (aposematic)
– secondary compounds in plants to defend herbivore predation
flower color & structure to promote insect & mammal pollination
d. ecological succession
primary vs secondary
pioneer species
climax community
3. Ecosystems
a. Energy flow/production = amount of energy lost at each trophic level
trophic levels = primary producers, primary consumers, secondary consumers,
tertiary consumers, detritivores & decomposers
ecological pyramids (pyramids of energy, biomass, numbers)
food chains & food webs
b. Nutrient cycles – chemicals, reservoir, assimilation, release
cycles: water, carbon, nitrogen, phosphorus
4. Biomes – distinguish between a. tropical rainforest
b. temperate grassland
c. temperate deciduous forest
d. desert
e. taiga
f. tundra
g. freshwater
h. marine
5. Human impact – examples
a. greenhouse effect / global warming
b. ozone deletion
c. acid rain
d. pollution (air, water, land)
biomagnificaion
eutrophication
e. desertification
f. deforestation – in class example
g. loss of species diversity
B. Labs
1. Dissolved Oxygen Lab
Be sure to review the procedures and the conclusions, and understand:
a. how to measure primary productivity (photosynthesis)
measure rate of CO2 consumption
measure oxygen production
measure biomass production
b. factors that affect dissolved oxygen
temperature = temp = dissolved O2
photosynthesis = bright light = dissolved O2
decomposition = microbial respiration = consumes O2
turbulence = dissolved O2
c. difference between gross productivity & net productivity
gross productivity = how much CO2 fixed from air into sugars
net productivity = gross productivity (bottle in light) – respiration (bottle in dark)
C. Sample Multiple Choice Questions – Some of these questions are also
dependent on knowledge from other units which may not be covered yet.
1. All of the following are density-dependent factors that limit animal populations EXCEPT
(90:08)
A. weather
B. predation
C. birthrate
D. food competition
E. mortality
2. During the carbon cycle, which of the following carbon compounds would be utilized as an
energy source by heterotrophs? (90:36)
A. calcium carbonate
B. carbonic acid
C. organic molecules
D. carbon dioxide
E. carbon monoxide
3. All of the following statements concerning characteristics of predator-prey relationships are
correct EXCEPT:
A. A rise in the population of prey is often followed by a rise in the population of predators.
B. A rise in the population of predators is followed by a decrease in the population of prey.
C. Camouflage is an adaptation that protects prey.
D. The production of large numbers of offspring within very short periods of time ensures
the survival of some prey populations.
E. The population of predators most often eliminates the population of prey.
4. Which of the following is true about secondary consumers in an ecosystem? (90:31)
A. They eat only plants.
B. They are eaten by primary consumers.
C. They are smaller and weaker than are primary consumers.
D. They are fewer in number than are primary consumers.
E. They contain the greatest total biomass in the system.
5. In the nitrogen cycle, the transformation of gaseous nitrogen into nitrogen-containing
compounds is performed primarily by (90:35)
A. fungi
B. bacteria
C. green plants
D. herbivores
E. carnivores
A. tropical rain forest
B. taiga
C. arctic tundra
D. temperate grassland
E. desert
#6- 10 Use the choices below.
A. Tropical Rainforest B. taiga C. tundra d. Grassland e. desert
6. Permafrost; temperatures range from approximately -50°C to +25°C; a growing season of 60
days or less (90:91)
7. Over 10 inches of precipitation per year; long, cold winters and short summers; dominant
vegetation is gymnosperm (90:92 modified)
8. Lack of water common in summer; seasonal temperature variations; maintained by periodic
fires (90:93)
9. Less than 10 inches of precipitation per year; extremes of hot and cold throughout the year;
large daily temperature variations (90:94)
10. This biome has the greatest diversity of species. (99:80)
11. Which point on the curve in the diagram above best represents the carrying capacity of the
environment for the population shown. (99:01)
A. A
B. B
C. C
D. D
E. E
Questions 12–14. refer to the food web below. (90:106-108)
12. Which of the following organisms is most likely to
be located at the apex of the pyramid of biomass?
(90:106)
A. grass
B. grasshopper
C. snake
D. mouse
E. hawk
13. All of the following statements about the diagram are correct EXCEPT: (90:107)
A. The grasshopper is an herbivore.
B. Only two trophic levels are depicted.
C. The mouse and grasshopper are at the same trophic level.
D. The grass is a producer.
E. All of the organisms except grass are consumers, regardless of position.
14. The organic and inorganic materials in all the organisms in the diagram will eventually return
to the environment by the action of (90:108)
A. decomposers
B. producers
C. primary consumers
D. secondary consumers
E. top carnivores
15. Which of the following best explains why there are seldom more than five trophic levels in a
food chain? (94:11)
A. Most carnivores function at more than one trophic level.
B. Trophic levels above this number contain too many individuals.
C. Top carnivores are too few in number to prey effectively.
D. The ecosystem contains too much biomass.
E. Energy is lost from each trophic level.
Questions 16-19. The illustrations below show the age and sex of the human populations in
Country 1 and Country 2. The ages are grouped by 5-year classes, and the sexes are
represented separately. The percentages in the different age classes are shown by the relative
widths of successive horizontal bars. (94:109-112)
16. In Country 1, approximately what percentage of the individuals were younger than fifteen
years of age? (94:109)
A. 10%
B. 21%
C. 42%
D. 52%
E. It cannot be estimated from the graph.
17. Which of the following best approximates the ratio of males to females among individuals
below fifteen years of age? (94:110)
Country 1 Country 2
A. 1 : 1 1 : 1
B. 0.75 : 1 0.75 : 1
C. 0.5 : 1 0.5 : 1
D. 1 : 1 0.5 : 1
E. 0.75 : 1 1 : 1
18. If, in Country 1, infant mortality declined and the birth rate remained the same, then initially
the population would be expected to (94:111)
A. be more evenly distributed among the age classes
B. be even more concentrated in the young age classes
C. stabilize at the illustrated level for all age classes
D. increase in the oldest age classes
E. increase in the median age classes
19. Over the next 10-15 years, the stabilization of Country 1’s population at its current size
would require that (94:112)
A. infant mortality be reduced to about half the present level
B. the death rate be reduced drastically
C. each couple produce fewer children than the number required to replace themselves
D. about 15 years be added to the life expectancy of each person
E. couples have an average of only 3 children
Questions 20–21. The graph below shows changes in a population of wild sheep that were
introduced to the island of Tasmania in the early 1800s. (99:117–120)
20. The type of population growth represented by
that portion of the graph line enclosed in the
bracket is most accurately termed (99:117)
A. stable
B. exponential
C. density-dependent
D. arithmetic
E. decelerating
21. The graph indicates that the sheep population most likely is (99:118)
A. growing in excess of its carrying capacity, since fluctuations in population size occurred
after 1850
B. headed for extinction because of the population explosion about 1930
C. regulated by density-independent factors, because there appears to be about a 10-year
cycle of sharp declines in size
D. shifting from K-selected strategy to an r-selected strategy
E. stable after 1850 under the effects of density-dependent regulating factors
D. Sample Free Response Questions
1. 2006:2
According to fossil records and recent published observations, two species of leaf-eating
beetles (species A and B) have existed on an isolated island in the Pacific Ocean for over
100,000 years. In 1964 a third species of leaf-eating beetle (species C) was accidentally
introduced on the island. The population size of each species has been regularly monitored as
shown in the graph above.
a. Propose an explanation for the pattern of population density observed in species C.
b. Describe the effect that the introduction of beetle species C has had on the population
density of species A and species B. Propose an explanation for the patterns of
population density observed in species A and in species B.
c. Predict the population density of species C in 2014. Provide a biological explanation for
your prediction.
d. Explain why invasive species are often successful in colonizing new habitats.
2. 2004:4
Organisms rarely exist alone in the natural environment. The following are five examples of
symbiotic relationships.
Plant root nodules
Digestion of cellulose
Epiphytic plants
AIDS (acquired immune deficiency syndrome)
Anthrax
Choose FOUR of the above and for each example chosen,
a. identify the participants involved in the symbiosis and describe the symbiotic
relationship, and
b. discuss the specific benefit or detriment, if any, that each participant receives from the
relationship.
3. 2007:3
Compared with other terrestrial biomes, deserts have extremely low productivity.
a. Discuss how temperature, soil composition, and annual precipitation limit productivity in
deserts.
b. Describe a four-organism food chain that might characterize a desert community, and
identify the trophic level of each organism.
c. Describe the results depicted in the graph. Explain one anatomical difference and one
physiological difference between species A and B that account for the CO2 uptake
patterns shown. Discuss the evolutionary significance of each difference.
4. 2007:4
The energy flow in ecosystems is based on the primary productivity of autotrophs.
a. Discuss the energy flow through an ecosystem and the relative efficiency with which it
occurs.
b. Discuss the impact of the following on energy flow on a global scale
Deforestation
Global climate change
5. 2008:2
Consumers in aquatic ecosystems depend on producers for nutrition.
a. Explain the difference between gross and net primary productivity.
b. Describe a method to determine net and gross primary productivity in a freshwater pond
over a 24-hour period.
In an experiment, net primary productivity was measured, in the early spring, for water sample
taken from different depths of a freshwater pond in a temperate deciduous forest.
c. Explain the data presented by the graph, including a description of the relative rates of
metabolic processes occurring at different depths of the pond.
d. Describe how the relationship between net primary productivity and depth would be
expected to differ if new data were collected in mid-summer from the same pond.
Explain your prediction.